1. Technical Field
The present disclosure relates to a system and a method for transmitting network packets adapted for transmitting isochronous packets of multimedia streams.
2. Description of Related Art
With development of digital home appliances, applications of enjoying high quality real-time video services through a network are greatly increased. For example, a residential Ethernet is used to connect every room in the home, and multimedia data in a digital versatile disc (DVD) player located in a bedroom can be viewed via a television located in a living room in real-time through network streaming. The conventional Ethernet applies a carrier sense multiple access communication protocol with collision detection (CSMA/CD) to compete with each other for the same bandwidth to transmit packets. Such mechanism is not suitable for transmitting time-sensitive packets such as video and audio files since a transmitting time is liable to be delayed to decrease a quality of service (QoS). Therefore, under an environment of limited bandwidth and in case that file transmission trends to be more complicated, to effectively adjust the bandwidth to increase a system performance is an important issue.
An institute of electrical and electronics engineers (IEEE) 802.1 p/q is a standard established for resolving the transmission QoS issue, in which a tag of 4 bytes is added in a header of layer 2. The front two bytes are fixed to be 8100H, which serve as an identification of an Ethernet packet type. The first 3 bits of the next 2 bytes are used for storing priorities. A transmission packet can be classified into 8 priorities, and the higher priority denotes a higher sending priority. If the priorities of isochronous packets of a video/audio file are increased, the transmission delay of the conventional Ethernet due to that all of the packets have the same priority can be ameliorated.
A U.S. Patent application No. US2007/0025385 provides a concept of time slot to monitor an applicable bandwidth of the network, and a counter is used to count a time interval for transmitting the isochronous packets. When the applicable bandwidth is relatively great, a relatively fast bit rate is used to transmit the isochronous packets, and when the applicable bandwidth is relatively small, a relatively slow bit rate is used to transmit the isochronous packets.